1. Field of the Invention
The present invention relates to an ultrasound transducer, and more particularly to an ultrasound transducer that is used for detecting the existence of an object or measuring the distance between the object and the ultrasound transducer. More particularly, the present invention relates to an ultrasound transducer that has the best-optimized structure for wide ultrasound wave transmission extent.
2. Description of Related Art
Ultrasound transducers are used for various applications that need to detect objects. Typical applications of the ultrasound transducers include detection and range finding of the targeted objects. For instance, obstacle detection for the tail of an automobile through the ultrasound waves is a common application. In many applications, the ultrasound transducers employ the piezoelectric elements to generate ultrasound waves for the aforementioned detecting functions. In most circumstances, the same ultrasound transducer is usually used as an ultrasound transmitter and an ultrasound receiver. In other words, the same ultrasound transducer is deemed a dual-function device that implements both ultrasound wave transmission for scanning and/or range finding purposes and reflected ultrasound wave receipt.
In both transmitting and receiving operation modes, the shapes of the transmitting and receiving fields of an ultrasound transducer always greatly affect the applications of the ultrasound transducer. For instance, in the purpose monitoring the nearby surroundings around the tail of an automobile, both the ultrasound coverage fields of transmitting and receipt need to be shaped appropriately to achieve the best operation. Generally, both the transmitting and receipt coverage fields need a wide horizontal extent shaping and a narrow vertical extent shaping. The wide horizontal coverage field pattern efficiently increases the effectively monitoring angular extent. The narrow vertical coverage field pattern efficiently reduces interference of reflected ultrasound waves.
The shape of the coverage field under the receiving operation mode of an ultrasound transducer for an automobile tail monitoring system is required to be substantially identical or similar to that under the transmitting operation mode thereof. For applications on cameras or the like, the same requirement is needed.
To reach the aforementioned requirements, a conventional method is increases the operation frequency extent to reduce the vertical coverage field pattern, which probably reduces the horizontal coverage field pattern disadvantageously. Thus, the horizontal detection blind zone increases. Therefore, the method cannot completely conform to the requirements.
Another conventional method is to change and adjust the shape design of a cup-shaped casing of the ultrasound transducer to form various internal opening such as rectangular, elliptical, trapezoidal and teardrop-like cross sections, which intends to achieve the desirable ultrasound coverage fields. However, the ultrasound transducers do not maintain a sufficient horizontal coverage field while effectively reducing the vertical coverage field.
For instance, FIG. 1A shows a cross sectional view of an ultrasound transducer disclosed in JP Patent No. 9-284896. In FIG. 1A, the ultrasound transducer (1) has a cup-shaped casing (12) and an internal opening (10) defined in the cup-shaped casing (12). The internal opening (10) has a cross section being similar to two intersecting ellipses. A piezoelectric element (14) is mounted in a bottom of the cup-shaped casing (12). With reference FIG. 1B, the ultrasound coverage field pattern distributions in horizontal and vertical directions are 54 degrees and 50 degrees at −3 dB. Although using such cup-shaped casing (12) widens the horizontal ultrasound coverage field and narrows the vertical ultrasound coverage field, the shape of the vertical ultrasound coverage field is undesirable.
To overcome the shortcomings, the present invention provides an ultrasound transducer with a dumbbell-shaped chamber to mitigate or obviate the aforementioned problems.